Method and apparatus for determining at least one characteristic value of movement of a body

ABSTRACT

With the apparatus of the invention, any acceleration/deceleration in the direction of movement is sensed by a pendulum. Electrical signals derived therefrom are used for solving the differential equation of oscillation of the pendulum for determining the acceleration, velocity and/or the distance covered by the moved body within a desired time period.

1. Field of the Invention

The invention relates to a method and apparatus for determining theacceleration, the velocity and/or distance covered of a moved or movingbody, for instance in respect to a running or jogging person. Theapparatus, to the invention may also be used for determining a change ofan angle of inclination of a sensor applied to a moved body, forinstance, to an automobile.

2. State of the Art

(a) Inertia navigation systems have become known which calculate thedistance covered by integration of determined acceleration values. Thesesystems use cardanly (freely movable) suspended platforms maintainedstable by gyros in their position with respect to a horizontal plane.Pendulums may be used as acceleration transducers, as disclosed in theGermon Offenlegungsschrift No. 29 20 44 3. In particular, a pendulumprovided with an inertia mass is maintained in its zero position by anelectromagnetically generated torque. Exciting current necessary togenerate this torque serves as a measure of the acceleration acting uponthe inertia mass.

(b) Furthermore, so-called strap down navigation apparatus have becomeknown which are provided with acceleration transducers secured to amoved body. The apparatus uses the determined acceleration values anddisplacement information of a gyro to compute, in combination with aco-ordinate transformation computer, the velocity and covered distancevalues.

(c) Also, acceleration sensors have become known operating according tothe principle of linear displacement of an inertia mass and a coilprovided with a resetting spring and arranged within a magnetic field(see German Offenlegungsschrift No. 23 03 104). The voltage induced inthe coil upon the linear displacement is, after integration, a measureof the acceleration of the coil.

The inertia navigation systems mentioned under (a), as well as thenavigation systems of (b), are of complex and expensive mechanicaldeisgn and require extensive and complex calculations, regulations andcontrols.

The apparatus explained under (c) is subject to relatively largefriction forces in view of the mechanical guidance of the linearly movedinertia mass. It is, therefore, not adapted for measuring lownon-periodic accelerations. Furthermore, such an apparatus issusceptible to considerable errors if the acceleration sensors are notsecured to the moved body in an exactly horizontal manner.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method andapparatus for measuring and determining the acceleration, the velocityand/or the distance covered in respect to a body moved essentiallylinearly and for directly displaying the determined values.

It is a further object of the invention to provide a method andapparatus which are particularly adapted for moving sportsmen and whichdetermine and display acceleration, velocity and/or covered distance.

Still another object of the invention is to provide an apparatus formeasurements having a high sensivity at low acceleration.

Still another object of the present invention is to provide an apparatushaving a compact, shock-insensitive design and low weight such that thecomplete apparatus is adapted to be attached to, and carried by, asportsman without affecting his or her movement.

It is another object of the present invention to provide an apparatushaving at least one vector of direction where any influence of anon-horizontal attachment to the body of the sportsman is compensated.

A still further object of the invention is a cost-effectiveimplementation.

These and other objects of the invention are achieved by an apparatusfor determining at least one characteristic value of movement(acceleration, velocity, distance covered) of a body comprising:

(a) a housing attachable to the body;

(b) a sensor device arranged in the housing and including a pendulumsuspended for free deflection in a direction opposite to the directionof movement of the body;

(c) a transducer device associated with the sensor device for generatingelectrical signals in response to the deflection of the pendulum;

(d) a processing device for receiving the electrical signals and forsolving the differential equation of oscillation of that pendulum on thebasis of the electrical signals, and for calculating the at least onecharacteristic value of movement; and

(e) a display device for displaying at least one characteristic value ofmovement calculated by the processing device.

With the apparatus according to the invention, there is eliminated thecomplex control circuit which is necessary with known accelerationtransducers for generating the restoring torque. Only an integration ofthe determined values is necessary which may be carried out by a digitalintegration computer provided anyway.

An apparatus according to the invention is preferably intended for usein connection with a human or animal body. By attaching the apparatus tothe body at a height corresponding to that of the center of gravity ofthe body, on the average, a stable vector of direction, with respect tothe vertical axis through the center of gravity, is accomplished in viewof the sense of equilibrium of the person or animal. This means that theperson generates, by his sense of equilibrium, a reference directionwhich eliminates the complex arrangement using gyros and controlnetworks.

The transducer or sensor of the apparatus according to the inventionuses an inductance coil fixed to a pendulum and is pivotally mountedsuch that the inertia mass is capable of aligning in the direction ofthe vertical axis in the absence of any acceleration/deceleration. Thus,the direction of the vector of acceleration, being perpendicular to thevertical axis will always be predetermined, independent of the angle ofattachment of the transducer to the body.

It should be noted that with no movement of the body, the transducer andsensor device are adapted to determine the angle of inclination by whichthe sensor is turned away from its rest position upon inclination of thebody.

The inhomogeneous linear differential equation for the oscillation ofthe pendulum is known as:

    (I) α+2ρ·α+ω.sub.o.sup.2 α+κ.sub.i sin α+=κ.sub.2 (a.sub.x ·cos α-a.sub.y sin α)

wherein:

α=angle of deflection

α=first derivative of the angle of deflection

α=second derivative of the angle of deflection

ρ₁ ω₁ κ_(i1) κ₂ ρ,ω_(o),κ₁,κ₂ =constants of the physical design of thependulum, and

a_(x), a_(y) =x- and y-components of acceleration determined by thephysical design of the pendulum.

For small angles of α, the y-component may be neglected since cos α˜1and sin α˜0.

This results in the simplified differential equation:

    (II) α+2ρα+ω.sub.o.sup.2 α=κ.sub.2 ·a.sub.x

From equation (II), the acceleration in the direction of movement a_(x)may be calculated provided that α and/or α is determined by appropriatesensor and transducer devices.

In view of its very low bearing friction, the transducer or sensor ofthe instant invention achieves a high sensitivity with very low errorseven with small amounts of acceleration.

Since any movement as well as any changes in the angle of inclinationmay be recognized, the sensor system according to the invention, isexcellently adapted for alarm systems, for instance, for automobiles.Furthermore, monitoring changes in the angle of inclination may beuseful in connection with buildings, such as bridges, towers or thelike.

By employing a moving coil system, which is commercially available andused in moving coil galvanometers, the manufacture of the apparatus,according to the invention, is extremely cost-effective. It isparticularly easy to provide the known moving coil system with aninertia mass.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b are a side view and a plane view of the sensor used withthe apparatus according to the invention;

FIGS. 1c and 1d illustrate an optical/electrical transducer means;

FIG. 1e illustrates a force measuring element;

FIG. 2 shows a block diagram of the electronic portion of the apparatusof the present invention;

FIG. 3 is a schematic diagram showing the movement of a pendulum uponacceleration;

FiG. 4 is a schematic diagram for explaining the use of the apparatusaccording to the invention for indicating a change of inclination of abody having an apparatus fixed thereto;

FIGS. 5a and 5b are a side view and a plane view similar to those ofFIGS. 1a and 1b of another embodiment of the apparatus of the invention;

FIGS. 6a and 6b are a side view and a plane view of a dampening deviceused in connection with the apparatus according to the invention;

FIG. 7 is a schematic diagram for illustrating the position of thecenter of gravity of a human body;

FIG. 8 is a schematic diagram illustrating how the apparatus accordingto the invention is attached to a human body;

FIGS. 9a to 9d are views of the overall apparatus of the presentinvention, and

FiG. 10 is a schematic block diagram showing the main units of theapparatus according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The method and apparatus according to the invention will now beexplained by way of example with reference to the drawings which showtwo embodiments of the present invention.

Referring first to FIG. 10, the apparatus, according to the invention,comprises a mechanical acceleration sensor unit 20 including a pendulum,a transducer unit 30 for converting a movement of the pendulum intoelectrical signals, a processing unit 40 such as a microprocessor, forinstance of the type 80 51 of Intel Corporation, for receiving theelectrical signals from the transducer 30 and processing the signalsaccording to the differential equation of oscillation, and an input anddisplay unit 50 for controlling the processing until 40 by actuating anyof various keys and for displaying results and other values processed orstored in the processing unit.

In implementing the principles of the present invention, in a preferredembodiment, the acceleration sensor unit and the transducer unit arecombined to from a sensor and transducer unit 100 shown in FIGS. 1a and1b.

It should be noted that all of the units illustrated in FIG. 10 arearranged in a housing 60 as will be described later in connection withFIGS. 9a to 9d. For simplicity, the housing is omitted in FIGS. 1a and1b and FIGS. 5a and 5b and the various elements of the apparatusaccording to the invention are shown in a more schematic manner.

Referring now to FIGS. 1a and 1b, the sensor for sensing an accelerationof a moved body or a change of inclination includes a pendulum 4provided with an inertia mass 5. The pendulum 4 is pivotally secured toa shaft 3 which extends horizontally within the housing 60 (FIG. 9c).The reference numeral 11 indicates a human body to which the apparatus,according to the invention, is attached. A permanent magnet 6 generatesa magnetic field 1 between pole shoes 7 and 8 and armature 9 which has acylindrical shape and has the shaft 3 as a central axis thereof. Thearmature 9 is fixed to the housing, as is the magnet 6. Between theinner circular surfaces of the pole shoes 7, 8 and the armature 9, anessentially circular air gap 10 is formed having a generally constantwidth. Thus there exists a homogeneous magnetic field 1 along most ofthe air gap 10.

An inductance coil 2 is rotatably mounted about the axis of shaft 3 andis secured to the pendulum 4 such that the coil 2 is moved within themagnetic field 1 existing in the air gap 10 whenever the pendulum 4 isdeflected upon movement of the body.

The operation of the sensor and transducer unit 100 is as follows (FIGS.3 and 4):

It is assumed that the apparatus according to the invention is fixed tothe body of a jogger and that it is desired to determine the velocityand the distance covered by the jogger. As soon as the body 11 resumesmovement, it is accelerated according to the direction vector 13. Thesame acceleration acts upon the inertia mass 5 in the direction of thedirection vector 12 which is opposite to the vector 13. Thus, thependulum 4 is deflected by an angle α from its rest position, indicatedby a vertical axis 16, with reference to a clockwise direction in FIG.1a. This results in a rotation of the inductance coil 2 by the angle α.When the coil 2 is rotating, the windings of coil 2 cut the field linesof the magnetic field 1 inducing a voltage 14 across its terminals. Therelationship between the angle α and the induced voltage is:

    u(t)˜dα/dt                                     (III)

As may be gathered from FIG. 3, the angle α is related to theacceleration as follows:

    α=arctan a/g                                         (IV)

where g is the acceleration of gravity. For small angles, αapproximately is:

    α=a/g                                                (V)

For larger angle deflections, the increase of the angle α is smallerthan the corresponding increase in acceleration a. This ensures a largeoverall measuring range with a high sensivity in the lower range. Thedeviation from linearity is determined by equation (IV). Such adeviation may be compensated by the processing unit 50 as will bedescribed below. By a proper design of the air gap 10, the inducedvoltage 14 can be made highly linearly as follows:

In the lower range of the angle α, the air gap width may be larger andis reduced with increasing α in inverse proportion in accordance withequation (IV). The deviation of linearity is thus compensated by themagnetic induction increasing with increasing angle α.

Considering equations (III) and (V), the amount of the induced voltage14 is in proportion to the change in acceleration a, i.e. in a change ofthe lengths of the direction vectors 12 and 13, respectively.Accordingly

    u(t)˜dα/dt˜da/dt                         (VI)

Integrating the induced voltage 14 once, there results an acceleration aaccording to the acceleration vectors 12 and 13, respectively. Thismeans that the acceleration a is in proportion to the pendulumdeflection angle α.

In order to attenuate any initial transient oscillation of the pendulum4, a dampening means may be provided. Such a dampening means may consistof a frame of electrically conductive material onto which the inductancecoil 2 is wound. This frame attenuates the movement of the pendulum 4due to the current induced in the frame upon movement of the pendulum.

An alternative dampening means is shown in FIGS. 6a and 6b, andcomprises a chamber 17 in which a plate 18 is moved upon deflection ofthe pendulum, by being fixed to the shaft 3. The attenuation is achievedby the pressure difference between the left and right portions (FIG. 6a)of the chamber 17 when the plate 18 is pivoted in a clockwise direction.This pressure difference is equalized slowly by a narrow gap 19 betweenthe lower edge of the plate 18 and the inner surface of the chamber 17.The extent of attenuation may be determined by properly selecting thewidth of gap 19.

As indicated earlier, appropriate means are necessary to measure eitherthe angle α of the deflection of the pendulum and/or its firstderivative α. With the preferred embodiment, α is measured by thevoltage 14 induced in coil 2 by means of inductivity. Alternatively, αmay be measured by a suitable optical/electrical transducer meansoperating on an analog or digital principal, such as coding discs 200(FIGS. 1c and 1d) arranged between light emitting device 201 and lightreceiving device 202, CCD devices, clock pulse counting means or thelike. Furthermore, α may be measured using inductively or capacitivelyoperating bridge circuits, Hall-sensors or piezo resistive transducers(shown in FIG. 1e and explained below).

It should be noted that the computing of the acceleration a aresimplified if both α and α is measured.

Referring to FIG. 2 the electronic section of the apparatus according tothe invention will be described.

The induced voltage 14 from the sensing and transducing unit 100 isapplied to the processing and operating system 101. FIG. 2 shows acentral processing unit CPU 22 in association with a RAM 23, a programmemory 24, a display unit 25, an interface unit 26 and an input unit 27.The induced voltage 14 from the sensor and transducer unit 100 isapplied to the CPU 22 through an A/D converter 21.

The input unit 27 may be provided with various keys for instructing theCPU 22 to perform various operational procedures. Any results and otherdesired values may be displayed by the display unit 25, or output forfurther evaluation via the interface 26.

The induced voltage 14 from the sensor and transducer unit 100 isapplied as an analog signal 32 to the A/D converter 21 through anamplifier 20. The CPU 22 determines, by a signal transmitted throughconnection 13, which of the inputs of the A/D converter is to receivethe input signals. The A/D converter 21 converts the analog input signal32 to a digital value 30 which is received by the CPU 22 at definedintervals Δt_(i) as instructed by the CPU 22 via control connection 33.At the beginning of a movement of the body, CPU stores a first valueα_(o) in RAM 23. During the next scan cycle, a digital valuecorresponding to an angle increment Δα is received by the CPU 22 and asecond digital value α₁ is stored in RAM 23, and so on. By repeatedadditions at defined time intervals Δt_(i), the integral of the inducedvoltage 14 is formed. The constant of integration is the result of theimmediately preceding integration. Any result calculated at a certaintime is the current acceleration of the moving body. If commanded by theinput unit 27, such a result may be supplied to the display unit 26 anddisplayed there. Also, this result may be output through interface 26for further evaluation.

As well-known to a person skilled in the art, the values for thevelocity and the distance covered may be computed through furtherintegrations according to the following formulae: ##EQU1## The computingwill be effected in a well-known manner by a control program stored in,program memory 24. A clock signal, as well as the timing signals fordetermining the time Δt_(i), will be generated by a clock generator 34.

Alternatively, as mentioned before, an apparatus according to theinvention may be used for determining a change in an inclination angle γif a body is turned from a first position into a different position.This situation is illustrated in FIG. 4. The integral of the inducedvoltage 14 is, according to equation (III), proportional to the angle γof rotation and the first integral results in the inclination γ. Such adevice may be used as an alarm device when attached to an automobile. Inoperation, any change of in the position of the car, for instance bylifting it at the front or the rear or by pushing or pulling it, willresult in a deflection of the pendulum, a generation of an inducedvoltage 14, and an output signal which may be used for actuating analarm means.

As shown in FIG. 2, further sensing and transducing units 103 havingdirection vectors arranged at predetermined angles to direction vector13 may be used. For each further sensing and transducing unit 103, thereis provided an amplifier 35, the analog output signal of which isapplied to the A/D-converter through inputs programmable by the CPU 22through connection 31. By means of the input unit 27, the CPU 22 may becontrolled such that the signals from all sensing and transducing unitsmay be stored in RAM 23 and displayed by unit 25.

FIG. 5 shows a further embodiment of the apparatus according to theinvention using two sensing and transducing units 100 and 103 combinedwith each other. There is only one magnetic circuit, as explained inconnection with FIGS. 1a and 1b, producing a magnetic field 10 in whichthere are provided an inductance coil 2 and a rotatable coil 53 aboutthe common shaft 3. Inductance coil 2 is secured to the pendulum 4bearing the inertia mass 50. The pendulum 51 is maintained in apredetermined position by a spring 52, at a predetermined angle θ to therest position 16 of the pendulum 4, as long as there is no accelerationY acting on the pendulum 51. Any accelerations of the pendulums 4 and 51result in induced voltages 14 and 54 as explained in connection with thefirst embodiment. As shown in FIG. 1e, as force measuring element 210,such as a piezo-resistance transducer, may be applied to the spring 52shown in FIG. 5a.

FIGS. 7 and 8 illustrate how the apparatus according to the invention isattached to the body of a jogger. Typically the apparatus is attached ata height corresponding to the position of the center of gravity 40 ofthe body. In view of the sense of equilibrium of the jogger on theaverage a reference direction 41 is established parallel to the groundsurface 42. Accordingly, axis 43 in the direction of the pendulum 4 inrest position.

FIGS. 9a to 9d shows the physical arrangement of the various units inthe housing 60. Preferably, attaching means 61 may be used to attachhousing 60 to the body of the jogger at the height of the center ofgravity, for instance by a belt or a clip. Alternatively, the apparatusmay be unitary with a piece of cloth. The arrow 62 shows the directionof movement and acceleration.

I claim:
 1. An apparatus for determining at least one characteristicvalue of movement (acceleration, velocity, distance covered) of a movingbody comprising:(a) a housing detachably mounted on said moving bodyindependent of a vertical direction of attachment to said moving body;(b) a sensor means arranged in said housing and including a pendulumsuspended in said housing for free deflection about a horizontal axis ina direction opposite to a direction of movement of said moving body; (c)a transducer means connected with said sensor means for generatingelectrical signals in response to any said deflection of said pendulum;(d) a processing means for continuously receiving said electricalsignals, for continuously solving a differential equation of oscillationof said pendulum based on said electrical signals and for continuouslycalculating said at least one characteristic value of movement; and (e)a display means for displaying said at least one characteristic value ofmovement calculated by said processing means.
 2. The apparatus of claim1, wherein said transducer means includes an inductance means secured tosaid pendulum for rotation in a magnetic field upon any deflection ofsaid pendulum for inducing a voltage, said magnetic field beinggenerated in an air gap in which said inductance means is moveable andwhich is formed by a magnetic means circularly arranged about an axis ofrotation of said inductance means, said induced voltage representingsaid deflection of said pendulum.
 3. The apparatus of claim 2, whereinsaid pendulum is biased by a restoring spring means for returning saidpendulum into a position in which said pendulum is maintained at adefined angle to a vertical axis in the absence of anyacceleration/deceleration of said body.
 4. The apparatus of claim 1 or2, further comprising at least one further sensor means arranged tosense a movement in a direction different from that of said sensor meansand arranged at a predetermined angle with respect thereto.
 5. Theapparatus of claim 4, wherein said at least one further sensor meanscomprises a further pendulum provided with a further inductance meansfor rotation with said further pendulum upon a deflection thereof andbiased to a rest position at a predetermined angle with respect to therest position of said pendulum by a spring means in an absence of anyacceleration/deceleration acting upon said further pendulum.
 6. Theapparatus of claim 2, wherein said pendulum is provided with a dampeningmeans.
 7. The apparatus of claim 2 wherein said air gap has a varyingwidth which is reduced in a direction of increasing deflection of saidpendulum.
 8. The apparatus of claim 1, wherein said processing meanscomprises:a microprocessor connected to said transducer means forreceiving said electrical signals, a program memory connected to saidmicroprocessor for storing a program for solving said differentialequation of oscillation, a clock generator connected to saidmicroprocessor for generating a system clock and time reference signals,a RAM means connected to said microprocessor for storing digital valuesderived from said electrical signals received from said transducingmeans and processed in said microprocessor, intermediate results andsaid at least one characteristic value calculated by saidmicroprocessor, and input means connected to said microprocessor forconditioning said microprocessor to execute portions of said programstored in said program memory.
 9. The apparatus of claim 8, wherein saidprocessing means further comprises an output means for outputting datastored in said RAM means for further processing thereof.
 10. Theapparatus of claim 1, wherein said housing has arranged at its topsurface said display means for displaying said at least onecharacteristic value of movement and selecting means for setting saidprocessing means to calculate one of said characteristic values ofmovement.
 11. The apparatus of claim 1, wherein said transducer meansare optical/electrical transducing means.
 12. The apparatus of claim 1,wherein said transducing means are force responsive means.
 13. Theapparatus of claim 1, wherein said transducer means generate electricalsignals in dependence on an angle α of any deflection of said pendulum.14. An apparatus for determining a change of angle of inclination of amoved body, comprising:a housing attached to said body independent of avertical direction of attachment; a sensor means arranged in saidhousing and inlcuding a pendulum suspended in said housing for freedeflection at least in one direction about a horizontal axis; atransducer means for generating electrical signals in response to anydeflection of said pendulum; and a processing means for receiving saidelectrical signals and for solving a differential equation ofoscillation of said pendulum based on said electrical signals and forcalculating said change of angle of inclination of said moved body. 15.The apparatus of claim 14, wherein said processing means generates anoutput signal whenever said change in angle of inclination exceeds apredetermined value.
 16. The apparatus of claim 14, wherein saidprocesisng means generates an output signal indicative of an amount ofchange of said angle of inclination.
 17. The apparatus of claim 14,wherein said transducer means are optical/electrical transducing means.18. The apparatus of claim 14, wherein said transducing means are forceresponsive means.
 19. A method for determining at least onecharacteristic value of movement (acceleration, velocity and distancecovered) of a body comprising the steps of:(a) sensing from a beginningof the movement a deflection about a horizontal axis pendulum secured tosaid body independent of a vertical direction of attachment; (b)generating electrical signals in resposne to any deflection of thependulum; (c) continuously solving a differential equation ofoscillation of said pendulum based on said electrical signals; (d)calculating said at least one characteristic value of movement based ona solution of said differential equation of oscillation of saidpendulum; and (e) selectively outputting said at least onecharacteristic value of movement.